1. Field of the Invention
The present invention relates to a reducer with an internally meshing planetary gear mechanism and a device incorporating the reducer used for driving a machine in a high-precision control system, such as a joint controller of industrial robots, an automatic tool exchanger, and the like.
2. Description of the Related Art
FIG. 6 shows one example of a conventional reducer with an internally meshing planetary gear mechanism (hereinafter simply referred to as “reducer”) 10 used for driving a machine in a high-precision control system, such as a joint controller of industrial robots or an automatic tool exchanger (Japanese Patent Laid-Open Publication No. 2001-187945). The reducer 10 is provided with a first flange 14A and a second flange 14B, and an internally meshing planetary reduction gear part (hereinafter simply referred to as “reduction gear part”) GS0. The first and second flanges 14A and 14B are disposed opposite each other inside a casing 12 and supported rotatably in the casing 12. The reduction gear part GS0 is disposed between the first and second flanges 14A and 14B. An input shaft 16 of the reduction gear part GS0 is supported rotatably on respective sides by the first and second flanges 14A and 14B.
The first and second flanges 14A and 14B of this reducer 10 are integrally and securely coupled to each other by a plurality of carrier bolts 18 and are rotatable relative to the casing 12.
The input shaft 16 of the reduction gear part GS0 is supported by the first and second flanges 14A and 14B via a pair of bearings 20A and 20B so that it is rotatable relative to the first and second flanges 14A and 14B. The input shaft 16 in this conventional example is a hollow shaft having a bore. On the outer surface of the input shaft 16 between bearings 20A and 20B are integrally formed eccentric bodies 22A, 22B, and 22C, which are offset from each other by a certain phase difference. Three external gears 26A, 26B, and 26C are respectively mounted around the eccentric bodies 22A, 22B, and 22C via roller bearings 24A, 24B, and 24C so that they can oscillatingly rotate. The three external gears 26A, 26B, and 26C mesh with an internal gear 28 that is integral with the casing 12. The teeth of the internal gear 28 are composed of roller-like pins (outer pins) 30.
Inner pin holes 32A, 32B, and 32C are bored in the three external gears 26A, 26B, and 26C respectively, and a tubular inner roller 34 extends through the holes 32A, 32B, and 32C. An inner pin 36 is inserted in this inner roller 34. The inner pin 36 is supported on respective sides by the first and second flanges 14A and 14B, so that drive power input to the input shaft 16 of the reduction gear part GS0 is transmittable to the outside with reduced speed through the first and second flanges 14A and 14B.
Although not shown, grease is provided in the reduction gear part GS0, and to prevent grease leakage, seals 38A and 38B are arranged inside the bearings 20A and 20B. Further, oil seals 40A and 40B are arranged between the casing 12 and the first and second flanges 14A and 14B, respectively.
While the conventional reducer 10 is lubricated with grease, oil lubrication would be preferable in respect of higher fluidity than grease, high seizure load, and easy and low-cost maintenance.
Contrary to the assumption that grease may simply be replaced by oil, however, the conventional reducer 10 with oil lubrication failed to achieve desired performance and product life.
Another problem was that the sealing structure for the grease lubrication system could not be used as it is for an oil lubrication system because of the difference in viscosity.